Firdaus Kanga is disabled, gay and a devotee of the `wrong' religion in Bombay. But on the set of `Sixth Happiness', the film about his upbringing in which he was persuaded to star as himself, he is getting the full celebrity treatment. James Rampton finds him making a nuisance of himself.

Firdaus Kanga is a man from Bombay who is just four feet tall. He has brittle bone disease, a condition which means that he cannot walk and that if he so much as sneezes he is in danger of breaking a rib. He is also a Parsee, a religious minority often ostracised in the city. To complete the full house, he is gay, which is illegal and competely unacceptable in Indian society.

Sixth Happiness, a fictionalised film about his upbringing, looks suspiciously like what is known in the trade as a "wheelchair movie" with an upbeat "triumph-over-adversity" message.

That's exactly what it isn't. It is in fact a bitter-sweet, witty, romantic, sometimes sexy account of the difficulties of growing up. It is a coming- of-age rather than a plucky-disabled movie. The classic one-line Hollywood pitch would be: "My Left Foot meets My Beautiful Laundrette meets The Tin Drum."

Kanga adapted his own novel, Trying to Grow, into this defiantly unsentimental screenplay. As if that wasn't enough, he also makes his acting debut as the lead, Brit Kotwal. It has to be said, the 38-year-old rises wonderfully to the steep challenge of playing an imaginary version of himself from the age of eight to 18.

Kanga was initially reluctant to play the part, but he was won over by the need for believability. It just proved impossible to find an experienced- enough actor who matched the specifications of Brit's character.

Tatiana Kennedy, the producer, "was very against having an able-bodied actor play someone disabled," she recalls. "I wouldn't have felt easy with that. There was simply no way of creating this disability, apart from binding someone's legs or using effects in post-production."

So Kanga was persuaded to do the job, and he is now getting the star treatment for his troubles. He is affectionately dubbed "the maharaja" on set. Minions dash around obeying his every command.

When we talk, Kanga is chewing a chocolate bar while perched on his bed in the air-conditioned Winnebago in central Bombay. He has just completed a scene in which a kindly librarian has carried him downstairs to the loo.

He is a magnetic man with an imperial Roman nose and lantern jaw. Irrepressibly twinkly and flirtatious, he revels in gossiping wickedly about, say, the dress sense of people on set. "I can be very exhausting," he admits with a cheeky smile. "I make a nuisance of myself, playing up, demanding two people to fan me so I don't faint. It's an excuse if you're an artist. I do need more concessions than others, but it's quite tempting to take advantage." He is clearly loving the attention.

All this has in no way distracted him from his film's aim. "What I find intensely annoying about the arts world is that disabled people are supposed to be `positive' - that's the key word stamped on everyone's forehead," he complains. "The able-bodied are allowed to express all their emotions - jealousy, passion, and the rest. Why can't we do that? Why do we have to be decent and victorious?

"I am interested in the process of growing up," he continues. "All children have their share of pain - whether it's from an alcoholic father or a divorce. This is a story about growing up, not triumph over disability. Yes, it's about being gay and disabled, but it's not about the horror of being those things. There is pain, but it's the pain of being a human being rather than a disabled person. If just one disabled person sees it and thinks, `someone has told my story and it's not false,' that would bring me great joy."

Kanga is not afraid to castigate the able-bodied for their often patronising view of the disabled. "The image of the super-crip is depressing and quite easy to play up to. Disabled people have to resist the idea that we have to be either the victim or the master. There is an endless need to simplify the fact of being disabled. People who get to know me see me as myself. Those who don't, see me as someone to be pitied."

Echoing the dictum "beware of pity", Kennedy chimes in: "What I most admire about Firdaus is that he deals with his own disability with a total lack of sentimentality. There is never a moment in the script when there is any self-pity. There is a restraint to the emotional pain in the piece."

The whole film is certainly underpinned by a keen sense of irony. Kanga's writing cleverly intermingles light and shade. When his Anglophile mother loses his father, for instance, Brit comments that she "took the blow like the British. She withstood the Blitz, but after that she was no longer glorious." Later on, a lover assures Brit he will one day be able to see how beautiful he is; to which Brit replies acerbically: "Sure ... in a fairground mirror."

Despite the laughs, Kanga has found acting a draining experience. "More tears are shed over answered prayers than unanswered ones," he says ruefully. "As a writer, you get so used to having things your own way. Acting is emotionally less lonely, but it's much more hassle."

Kanga doesn't envisage a long-term future in acting - although he jokes that he'd like to play either Lady Macbeth or Lady Bracknell. "I can't see that many roles for someone with brittle bone disease," he sighs. "I'm not interested in fringe theatre, which would only take me on as a token or as something exotic."

Still, he now has Sixth Happiness on his CV - no mean achievement.

"In the West, people have never seen India portrayed in this fashion before," says Hussein, himself from Lucknow. ""Films set here have either been about colonialism or maharajas and the Taj Mahal. There are hundreds of other stories to be told, and they're not all about British women being raped in Indian caves.

"There'll be a backlash in India. If you're disabled, you're supposed to be a good boy. If you're gay, you're supposed to shut up and hide under the pillow."

`Sixth Happiness' has its UK premiere in the London Film Festival next Friday at the National Film Theatre (0171-420 1122) at 4.15pm and 9pm.

London Film Festival preview: see page 12